- Can Heteroarenes/Arenes Be Hydrogenated Over Catalytic Pd/C Under Ambient Conditions?
-
Hydrogenation of over a dozen aromatic compounds, including both heteroarenes and arenes, over palladium on carbon (Pd/C, 1–100 molpercent) with H2-balloon pressure at room temperature is reported. Analyses using pyridine as a model substrate revealed that acetic acid was the best solvent, as using only 1 molpercent Pd/C provided piperidine quantitatively. Substrate scope analysis and density functional theory calculations indicated that reaction rates are highly dependent on frontier molecular orbital characteristics and the steric bulkiness of substituents. Moreover, the established method was used for the concise synthesis of the anti-Alzheimer drug donepezil (Aricept?).
- Tanaka, Nao,Usuki, Toyonobu
-
p. 5514 - 5522
(2020/07/24)
-
- Modular Syntheses of Phenanthroindolizidine Natural Products
-
A highly concise strategy for the total synthesis of phenanthroindolizidines was developed. The one-pot iterative Suzuki-Miyaura reaction of aryl boronic acids with ortho-bromoaryl N-methyliminodiacetate (MIDA) boronate followed by a second Suzuki-Miyaura reaction with a suitable pyridyl bromide provided ortho-aza-terphenyls. Subsequent saturation of the triple bond, treatment with mesyl chloride, and reduction of the resulting dihydroindolizidinium ring afforded the hexahydroindolizines. A final vanadium-catalyzed oxidative electrocyclization provided the desired alkaloids in only three column-separation operations.
- Jo, Young-In,Burke, Martin D.,Cheon, Cheol-Hong
-
p. 4201 - 4204
(2019/06/14)
-
- Practical Intermolecular Hydroarylation of Diverse Alkenes via Reductive Heck Coupling
-
The hydroarylation of alkenes is an attractive approach to construct carbon-carbon (C-C) bonds from abundant and structurally diverse starting materials. Herein we report a palladium-catalyzed reductive Heck hydroarylation of aliphatic and heteroatom-substituted terminal alkenes and select internal alkenes with an array of (hetero)aryl iodides. The reaction is anti-Markovnikov selective with terminal alkenes and tolerates a wide variety of functional groups on both the alkene and (hetero)aryl coupling partners. Additionally, applications of this method to complex molecule diversifications are demonstrated. Mechanistic experiments are consistent with a mechanism in which the key alkylpalladium(II) intermediate is intercepted with formate and undergoes a decarboxylation/C-H reductive elimination cascade to afford the saturated product and turn over the cycle.
- Gurak, John A.,Engle, Keary M.
-
p. 8987 - 8992
(2018/09/11)
-
- Dual cobalt-copper light-driven catalytic reduction of aldehydes and aromatic ketones in aqueous media
-
We present an efficient, general, fast, and robust light-driven methodology based on earth-abundant elements to reduce aryl ketones, and both aryl and aliphatic aldehydes (up to 1400 TON). The catalytic system consists of a robust and well-defined aminopyridyl cobalt complex active for photocatalytic water reduction and the [Cu(bathocuproine)(Xantphos)](PF6) photoredox catalyst. The dual cobalt-copper system uses visible light as the driving-force and H2O and an electron donor (Et3N or iPr2EtN) as the hydride source. The catalytic system operates in aqueous mixtures (80-60% water) with high selectivity towards the reduction of organic substrates (>2000) vs. water reduction, and tolerates O2. High selectivity towards the hydrogenation of aryl ketones is observed in the presence of terminal olefins, aliphatic ketones, and alkynes. Remarkably, the catalytic system also shows unique selectivity for the reduction of acetophenone in the presence of aliphatic aldehydes. The catalytic system provides a simple and convenient method to obtain α,β-deuterated alcohols. Both the observed reactivity and the DFT modelling support a common cobalt hydride intermediate. The DFT modelled energy profile for the [Co-H] nucleophilic attack to acetophenone and water rationalises the competence of [CoII-H] to reduce acetophenone in the presence of water. Mechanistic studies suggest alternative mechanisms depending on the redox potential of the substrate. These results show the potential of the water reduction catalyst [Co(OTf)(Py2Tstacn)](OTf) (1), (Py2Tstacn = 1,4-di(picolyl)-7-(p-toluenesulfonyl)-1,4,7-triazacyclononane, OTf = trifluoromethanesulfonate anion) to develop light-driven selective organic transformations and fine solar chemicals.
- Call, Arnau,Casadevall, Carla,Acu?a-Parés, Ferran,Casitas, Alicia,Lloret-Fillol, Julio
-
p. 4739 - 4749
(2017/07/10)
-
- An efficient synthesis of 2-alkylpyridines using an alkylation/double decarboxylation strategy
-
We have discovered a novel route for synthesising 2-alkylpyridines by exploiting the decarboxylation of pyridyl malonate esters. Herein we report the synthesis of a number of examples and describe how the reaction was discovered.
- Donald, Craig,Boyd, Scott
-
supporting information; experimental part
p. 3853 - 3856
(2012/08/13)
-
- Deoxygenation of pyridine N-oxides with dimethylthiocarbamoyl chloride
-
(Chemical Equation Presented) Treatment of pyridine N-oxides with dimethylthiocarbamoyl chloride in boiling acetonitrile effects chemoselective deoxygenation to pyridines.
- Ponaras, Anthony A.,Zaim, Oemer
-
p. 487 - 489
(2008/03/29)
-
- A general synthesis of alkylpyridines
-
The hydroboration of alkenes, followed by the coupling of the B-alkyl-9-borabicyclo[3.3.1]nonane derivatives with bromopyridines constitutes an efficient procedure for the attachment of functionalized alkyl chains to the pyridine nucleus.
- Iglesias, Beatriz,Alvarez, Rosana,De Lera, Angel R
-
p. 3125 - 3130
(2007/10/03)
-
- Anti-inflammatory furanones
-
New 5-hydroxy-2-furanone compounds having anti-inflammatory, immunosuppressive and anti-proliferative activity and are useful in treating psoriasis and modifying calcium homeostasis.
- -
-
-
- A Convenient Palladium-Catalyzed Coupling Approach to 2,5-Disubstituted Pyridines
-
2,5-Dibromopyridine has been found to undergo a regioselective palladium-catalyzed coupling reaction with terminal acetylenes and arylzinc halides to give the corresponding 2-alkynyl-5-bromo- and 2-aryl-5-bromopyridines, respectively, in 70percent-90percent isolated yields.To complement this chemistry, the triflate derived from 2-methyl-5-pyridinol was found to participate in a palladium-catalyzed reaction with terminal acetylenes leading to the corresponding 5-alkynyl-2-methylpyridines.These intermediates can be further manipulated to afford a broad range of 2,5-disubstituted pyridines.
- Tilley, Jefferson W.,Zawoiski, Sonja
-
p. 386 - 390
(2007/10/02)
-
- Synthese regioselective par voie organometallique de pyridines, 4-picolines et 3,5-lutidines substituees en 2 par un groupe insature et/ou fonctionnel
-
A regioselective one-pot synthesis of 2-substituted pyridine derivatives from N-alkoxycarboxylpyridinium salts and α-unsaturated organozinc compounds is described.Similarly, functional alkynyl organomagnesium compounds lead to 2-alkynyl-ω-functional pyridines, from which (E)-2-alkenyl or 2-alkyl-ω-functional pyridines can be obtained by partial or complete reduction.
- Al-Arnaout, A.,Courtois, G.,Miginiac, L.
-
p. 139 - 154
(2007/10/02)
-
- Structural Factors Affecting the Basicity of ω-Pyridylalkanols, ω-Pyridylalkanamides and ω-Pyridylalkylamines
-
The present paper describes the preparation by conventional methods (when not available commercially) and the pKa-determination of the α-, β- and γ-isomers of pyridylethanamide, 3-pyridylpropanamide, 4-pyridylbutanamide, 5-pyridylpentanamide, pyridylmethanol, 2-pyridylethanol, 3-pyridylpropanol, 4-pyridylbutanol, 5-pyridylpentanol, pyridylmethylamine, 2-pyridylethylamine, 3-pyridylpropylamine, 4-pyridylbutylamine, and 5-pyridylpentylamine.While a field effect accounts for many variations in pKa as a function of chain length, marked inductive effects are operative in some methyl and ethyl homologs.The pKa-decreasing influence of an intramolecular H-bond is also apparent in some lower homologs belonging to the α-series.
- Mayer, Joachim M.,Testa, Bernard
-
p. 1868 - 1884
(2007/10/02)
-
